The signal, coming from a point between the Pisces and Aries constellations, has been picked up three times by a telescope in Puerto Rico.

There are other explanations besides extraterrestrial contact that may explain the signal. New Scientist said the signal could be generated by a previously unknown astronomical phenomenon or even be a by-product from the telescope itself.

But the mystery beam has excited astronomers across the world.

“If they can see it four, five or six times it really begins to get exciting,” Jocelyn Bell Burnell of the University of Bath in western England told the magazine.

It was broadcast on the main frequency at which the universe’s most common element, hydrogen, absorbs and emits energy, and which astronomers say is the most likely means by which aliens would advertise their presence.

The potentially extraterrestrial signals were picked up through the SETI+home project, which uses programs running as screensavers on millions of personal computers worldwide to sift through the huge amount of data picked up by the telescope.